AES E-Library

AES E-Library

Non Linear Stiffness of the Loudspeaker Measured in the Evacuated Space

The impedance of the mechanical vibration system of the loudspeaker was measured in vacuo in order to remove the contributions of the radiation impedance of air. The Hooke constant k was evaluated by the use of calibrated weights and from the membrane displacements due to the force exerted by DC current in the voice coil. The resonant frequency was found to decrease with increasing non-linear Hooke constant, which is attributed to the effective mass of the vibration system, dependent upon elongation. The effective mass was evaluated from the fitting of measured and calculated loudspeaker impedance curve.